ASTACUS. 
ASTACUS, pi. Fabricius, Leach. 
CANCER, Linnaeus. 
HOMARUS, M. Edwards. ( postea .) 
Antennae interiores breves, bifidi ; exteriores longissimae, pedunculo fere cylindrico, appendice 
laminari dentiformi, intus dilatata, vix articulum ultimum pedunculi obtectenti. 
Palpi pediformes ante pedunculos antennarum extensi, articulis sex exsertis, ultimo acuminato, 
hispido. 
Pedes decern : par anticum crassissimum insequale, digitis valide tuberculatis ; paria secundum et 
tertium didactyli, quartum et quintum monodactyli ; ungues fasciculato-pilosi, curvati, obtusi. 
Abdomen sex-articulatum, segmentis ad latera in laminis latis complanatis terminantibus. 
Cauda pentapliylla laminis exterioribus versus terminum articulato-divisis, ad articulum acute 
dentatis. 
External antennae above and outside the internal. The laminar appendag'e tooth-shaped, 
dilated on the inner side and not quite covering the penultimate joint of the peduncle. The 
exterior pedipalpus pediform and produced forwards beyond the peduncles of the antennae. The 
five pairs of legs are very large, thick, and unequal ; the grasping edges of the thumb and finger 
in the larger tuberculated ; in the smaller toothed ; second and third pairs narrow, with two fingers 
on the last joint ; fourth and fifth with the last joint undivided. The carapace nearly cylindrical, 
the rostrum curved forwards and having several teeth on each side. The six segments of the 
abdomen terminate at each side with a broad flat flap ; last segment with a sharp tooth at each 
side ; outer laminte of the tail divided transversely at about one-third distance from the end, in a 
moveable joint, the edge of the lai'ger portion being sharply toothed. 
This genus, the principal member of which is our common Lobster , was included under the 
specific name of gammarus in the Linnaean genus Cancer. It is associated b} r Lamarck with the 
little-fresh water Lobster in the genus Astacus, our large edible crustacean being named A. marinus 
and our smaller one A.fiuviatilis. 
